18x24x1 Activated Carbon Particles A/C Furnace Air Filters, Steel Frame Replaces 18x24x1 sized disposable filters. The actual size of this filter is 17-3/4 x 23-3/4 x 7/8. They are interchangeable with 1" disposable filters. Ac Filter Usa is now offering Pure Carbon a/c Furnace Air Filters for eliminating odors in your home or office. We manufactured in sizes from 8 x 12 to 36 x 24 inch and thicknesses 1/2, 1 and 2 inch. Interchangeable with 1 disposable filters. They have a useful life until 12 months, depending on the Activity or the place of use. Our activated carbon filters consist of a durable non-woven polyester Base media infused with a naturally derived charcoal that is treated. With oxygen in order to open up millions of tiny molecular size pores The carbon atoms. Because of its LOW AIR RESISTANCE dont make your Central Air. Unit work harder. Friendly to environment. With a warranty satisfaction and 100% money back guarantee.